Revert "[llvm] Use range-based for loops (NFC)"

range-based loop should not be used here, as
fixupImmediateBr push_backs into the container.

http://lab.llvm.org/buildbot/#/builders/168
http://lab.llvm.org/buildbot/#/builders/74
http://lab.llvm.org/buildbot/#/builders/5
http://lab.llvm.org/buildbot/#/builders/239
http://lab.llvm.org/buildbot/#/builders/237
http://lab.llvm.org/buildbot/#/builders/236

This reverts commit fedc5973.